I. Field of the Invention
The present invention relates generally to the modification and control of the temperature of the body. More particularly, the invention relates to a method for controlling body temperature by heat transfer to a balloon.
II. Description of the Related Art
Organs in the human body, such as the brain, kidney and heart, are maintained at a constant temperature of approximately 37° C. Hypothermia can be clinically defined as a core body temperature of 35° C. or less. Hypothermia is sometimes characterized further according to its severity. A body core temperature in the range of 33° C. to 35° C. is described as mild hypothermia. A body temperature of 28° C. to 32° C. is described as moderate hypothermia. A body core temperature in the range of 24° C. to 28° C. is described as severe hypothermia.
Patients may require pre or post-operative cooling for a variety of reasons, including, for example, treatment of a malignant hypothermia crisis and induction of therapeutic hypothermia for neurosurgery.
Catheters have been developed which are inserted into the bloodstream of the patient in order to induce total body hypothermia. For example, U.S. Pat. No. 3,425,419 to Dato describes a method and apparatus of lowering and raising the temperature of the human body. The Dato invention is directed towards a method of inducing moderate hypothermia in a patient using a metallic catheter. The metallic catheter has an inner passageway through which a fluid, such as water, can be circulated. The catheter is inserted through the femoral vein and then through the inferior vena cava as far as the right atrium and the superior vena cava. The Dato catheter has an elongated cylindrical shape and is constructed from stainless steel.
Other less cumbersome catheters have been developed to provide cooling intravascularly. For example, a heat transfer element such as disclosed in U.S. Pat. No. 6,096,068, incorporated herein by reference in its entirety, may be placed in the feeding artery of an organ to absorb or deliver the heat from or to the blood flowing into the organ. The transfer of heat may cause either a cooling or a heating of the selected organ. The heat transfer element is small enough to fit within the feeding artery while still allowing a sufficient blood flow to reach the organ in order to avoid ischemic organ damage. By placing the heat transfer element within the feeding artery of an organ, the temperature of the organ can be controlled with less of an effect on the temperature of the remaining parts of the body. A similar heat transfer device, which is employed for whole body cooling and which may be disposed in the venous vasculature, is disclosed in U.S. application Ser. No. 09/373,112, also incorporated by reference in its entirety.
While the previously mentioned techniques provide significant thermal control, they require the insertion of a catheter into the vascular system to induce heat transfer between the catheter and the blood stream. This is a relatively invasive procedure, which has an associated level of risk.
Accordingly, it would be desirable to provide an effective, less invasive method and apparatus for heating or cooling all or part of a patient's body. It would also be desirable to provide an effective, less invasive method and apparatus for heating or cooling all or part of a patient's body that could be employed in emergency situations, such as on an ambulance.